Pointing Electronic Device with Fast Start-Up Recovery and Corresponding Method

1. A pointing electronic device, comprising: an accelerometer sensor, configured to generate an acceleration signal indicative of accelerations acting on the pointing electronic device; a gyroscope sensor, configured to generate a gyroscopic signal indicative of angular rates of rotation of the pointing electronic device; a sensor fusion processing stage, coupled to the accelerometer sensor and gyroscope sensor, configured to generate an orientation estimation quantity indicative of an orientation of the pointing electronic device about a longitudinal axis based on a sensor fusion algorithm comprising joint processing of the acceleration signal and gyroscopic signal; a pointing determination stage, configured to: implement an orientation-compensation of the gyroscopic signal as a function of the orientation estimation quantity to determine an orientation-compensated gyroscopic signal; and generate screen-frame displacement data corresponding to 3D-space movements of the pointing electronic device based on the orientation-compensated gyroscopic signal; and a first processing block, configured to: store past values of the acceleration signal, during a time interval, preceding start-up, in which the accelerometer sensor is in a power-on mode and the gyroscope sensor is in a power-off mode; and upon start-up after pointing operation by the pointing electronic device is enabled, retrieve and process the stored past values of the acceleration signal to generate processed acceleration data, for use by the sensor fusion processing stage to initialize the sensor fusion algorithm and generate a starting value of a roll estimation quantity.

2. The device according to claim 1 , wherein the first processing block comprises a hardware storage unit configured to store the past values of the acceleration signal.

3. The device according to claim 1 , wherein the first processing block is configured to generate the processed acceleration data by: determining an average of the stored past values of the acceleration signal; or implementing a low-pass filtering of the stored past values of the acceleration signal.

4. The device according to claim 1 , wherein the first processing block is configured to: determine whether a shaking condition of the pointing electronic device is occurring, based on the processing of the stored past values of the acceleration signal; and cause the sensor fusion processing stage to initialize the sensor fusion algorithm based on: the acceleration signal, if the shaking condition is not occurring; or the processed acceleration data if the shaking condition is occurring.

5. The device according to claim 4 , wherein the first processing block is configured to determine whether the shaking condition is occurring by: computing a variance of the acceleration signal; and determining that the shaking condition is occurring if the computed variance is higher than a certain threshold.

6. The device according to claim 1 , further comprising a second processing block, configured to: modify a value of a weight coefficient assigned to the acceleration signal in the sensor fusion processing stage and thus an importance assigned to the acceleration signal in the generation of the starting value of the roll estimation quantity.

7. The device according to claim 6 , wherein the second processing block is configured to: estimate a shaking intensity associated with a shaking condition of the pointing electronic device, based on the joint processing of both the acceleration signal and the gyroscopic signal; and modify the value of the weight coefficient as a function of the estimated shaking intensity.

8. The device according to claim 7 , wherein the weight coefficient is increased based on the estimated shaking intensity with respect to a default value for standard operating conditions.

9. The device according to claim 8 , wherein the second processing block is configured to: modify the value of the weight coefficient when the estimated shaking intensity is higher or equal than a threshold; and set the weight coefficient to the default value, when the estimated shaking intensity is lower than the threshold.

10. The device according to claim 8 , wherein the second processing block is configured to set back the weight coefficient to the default value after a given time interval after start-up.

11. The device according to claim 6 , further comprising a filtering block, at an output of the sensor fusion processing stage, configured to filter the roll estimation quantity before the roll estimation quantity is used in the pointing determination stage, during a time interval after start-up in which the value of the weight coefficient is modified.

12. The device according to claim 11 , wherein the filtering block is configured to implement a low-pass filtering of the roll estimation quantity.

13. The device according to claim 1 , further comprising a communication interface unit configured to transmit the screen-frame displacement data to a host apparatus having a display, wherein the screen-frame displacement data are configured to control movement of a displayed element on a screen frame of the display.

14. An electronic system comprising: a pointing electronic device, comprising: an accelerometer sensor, configured to generate an acceleration signal indicative of accelerations acting on the pointing electronic device; a gyroscope sensor, configured to generate a gyroscopic signal indicative of angular rates of rotation of the pointing electronic device; a sensor fusion processing stage, coupled to the accelerometer sensor and gyroscope sensor, configured to generate an orientation estimation quantity indicative of an orientation of the pointing electronic device about a longitudinal axis based on a sensor fusion algorithm comprising joint processing of the acceleration signal and gyroscopic signal; a pointing determination stage, configured to: implement an orientation-compensation of the gyroscopic signal as a function of the orientation estimation quantity to determine an orientation-compensated gyroscopic signal; and generate screen-frame displacement data corresponding to 3D-space movements of the pointing electronic device based on the orientation-compensated gyroscopic signal; a first processing block, configured to: store past values of the acceleration signal, during a time interval, preceding start-up, in which the accelerometer sensor is in a power-on mode and the gyroscope sensor is in a power-off mode; and upon start-up, retrieve and process the stored past values of the acceleration signal to generate processed acceleration data, for use by the sensor fusion processing stage to initialize the sensor fusion algorithm and generate a starting value of a roll estimation quantity after pointing operation by the pointing electronic device is enabled; and a first communication interface unit configured to transmit the screen-frame displacement data; and a host apparatus, coupled to the pointing electronic device, and comprising: a second communication interface, configured to: communicate with the pointing electronic device; and receive the screen-frame displacement data; a display defining a screen frame; and a main controller, configured to control movement of a displayed element on the screen frame of the display according to the screen-frame displacement data received by the second communication interface.

15. A method for generating screen-frame displacement data based on 3D-space movements of a pointing electronic device, the method comprising: generating an orientation estimation quantity indicative of an orientation of the pointing electronic device about a longitudinal axis based on a sensor fusion algorithm comprising joint processing of an acceleration signal, indicative of accelerations acting on the pointing electronic device, and of a gyroscopic signal, indicative of angular rates of rotation of the pointing electronic device; implementing an orientation-compensation of the gyroscopic signal as a function of the orientation estimation quantity to determine an orientation-compensated gyroscopic signal; generating the screen-frame displacement data corresponding to the 3D-space movements of the pointing electronic device based on the orientation-compensated gyroscopic signal; storing past values of the acceleration signal, during a time interval, preceding start-up, in which the acceleration signal is active and the gyroscopic signal is inactive; and upon start-up after pointing operation by the pointing electronic device is enabled, retrieving and processing the stored past values of the acceleration signal to generate processed acceleration data, for initializing the sensor fusion algorithm and generating a starting value of a roll estimation quantity.

16. The method according to claim 15 , further comprising increasing a speed of recovery of an initial orientation estimation error in a time interval immediately following start-up, by modifying a value of a weight coefficient assigned to the acceleration signal in the sensor fusion algorithm and thus an importance assigned to the acceleration signal in the generating the starting value of the roll estimation quantity.

17. The method according to claim 16 , wherein modifying the value of the weight coefficient comprises increasing the weight coefficient based on an estimated shaking intensity with respect to a default value for standard operating conditions, in order to allow for a faster recovery of the initial orientation estimation error.

18. The method according to claim 17 , wherein modifying the value of the weight coefficient comprises setting back the weight coefficient to the default value after a given time interval after start-up.

19. The method according to claim 15 , wherein the processed acceleration data is generated by: determining an average of the stored past values of the acceleration signal; or implementing a low-pass filtering of the stored past values of the acceleration signal.

20. The method according to claim 15 , further comprising: determining whether a shaking condition of the pointing electronic device is occurring, based on the processing of the stored past values of the acceleration signal; and initializing the sensor fusion algorithm based on: the acceleration signal, if the shaking condition is not occurring; or the processed acceleration data if the shaking condition is occurring.